Boomwhacker 7-note Diatonic Bass Set description:

These Tuned Percussion Tubes are brightly coloured plastic tubes that are tuned by length to musical notes. They are affordably priced and easy to play. The standard or higher octave ranges in length from about 1 to 2 feet. The bass octave ranges from about 2 to 4 feet. The 1 3/4" diameter is a comfortable size to hold for young children and adults.